In the dyeing, screen printing, stenciling, and similar treatment of a textile in production the treatment liquid must be applied across the full width of the goods, over a distance that can be as great as 5 m. It is therefore necessary that the flow of the treatment liquid be controlled accurately so that no one region of the goods receives more liquid than another. This uniformity of flow is rarely achieved.
In addition it is extremely difficult when a thick foam or such liquid is being applied to achieve even flow. The liquid itself does not flow well and has little hydrostatic pressure because of its viscosity. Such foaming or viscous treatment liquids are, however, fairly common.
These problems are further all complicated with today's wide goods and high treatment speeds. When the goods are wide and moving fast it is almost impossible to apply a uniform coat of the liquid to them, a problem which is compounded when the liquid must be applied lightly or in a thin layer and when the liquid is highly viscous.